Disposable products such as facial tissue, sanitary tissue, paper towels, and the like are typically made from one or more webs of paper. If the products are to perform their intended tasks, the paper webs from which they are formed must exhibit certain physical characteristics. Among the more important of these characteristics are strength, softness, and absorbency. Strength is the ability of a paper web to retain its physical integrity during use. Softness is the pleasing tactile sensation the user perceives as the user crumples the paper in his or her hand and contacts various portions of his or her anatomy with the paper web. Softness generally increases as the paper web stiffness decreases. Absorbency is the characteristic of the paper web which allows it to take up and retain fluids. Typically, the softness and/or absorbency of a paper web is increased at the expense of the strength of the paper web. Accordingly, papermaking methods have been developed in an attempt to provide soft and absorbent paper webs having desirable strength characteristics.
U.S. Pat. No. 3,301,746 issued to Sanford et al. discloses a paper web which is thermally pre-dried with a through air-drying system. Portions of the web are then impacted with a fabric knuckle pattern at the dryer drum. While the process of Sanford et al. is directed to providing improved softness and absorbency without sacrificing tensile strength, water removal using the through-air dryers of Sanford et al. is very energy intensive, and therefore expensive.
U.S. Pat. No. 3,537,954 issued to Justus discloses a web formed between an upper fabric and a lower forming wire. A pattern is imparted to the web at a nip where the web is sandwiched between the fabric and a relatively soft and resilient papermaking felt, U.S. Pat. No. 4,309,246 issued to Hulit et al. discloses delivering an uncompacted wet web to an open mesh imprinting fabric formed of woven elements, and pressing the web between a papermaker's felt and the imprinting fabric in a first press nip. The web is then carried by the imprinting fabric from the first press nip to a second press nip at a drying drum. U.S. Pat. No. 4,144,124 issued to Turunen et al. discloses a paper machine having a twin-wire former having a pair of endless fabrics, which can be felts. One of the endless fabrics carries a paper web to a press section. The press section can include the endless fabric which carries the paper web to the press section, an additional endless fabric which can be a felt, and a wire for patterning the web.
PCT Publication WO95/17548 having a US priority date of Dec. 20, 1993 and published Jun. 29, 1995 in the name of Ampulski et al.; and PCT Publication WO 96/00813 having a US priority date of Jun. 29, 1994 and published Jan. 11, 1996 in the name of Trokhan et al. disclose papermaking methods employing dewatering felt layers.
Embossing can be used to pattern a web. However, embossing the web after the web is dried can disrupt fiber bonds, and ultimately decrease the strength of the web. While suitable methods of making paper webs are disclosed in the art, paper scientists continue to search for even better methods for making patterned paper structures economically and with increased strength, without sacrificing softness and absorbency.
Accordingly, one object of the present invention is to provide a method for dewatering and molding a paper web.
Another object of the present invention is to provide a method of enhancing water removal from a web during pressing of the web.
Another object of the present invention is to press a web and an imprinting member between three felt layers in order to pattern the web and enhance water removal from the web.
Another object of the present invention is to provide a non-embossed patterned paper web having a relatively high density continuous network, and a plurality of relatively low density domes dispersed throughout the continuous network.